The project was initiated to study those changes in gene expression which may be critical to neoplastic and malignant transformation using the hamster embryo cell model in combination with quantitative two-dimensional electrophoresis. Results obtained to date include: (1) although bisulfite has been shown to be a potent transformation agent in vitro, acute bisulfite treatment (15 minutes, 10 micrograms/milliliter) at neutral pH had no qualitative effect on gene expression; (2) similarly gene expression during "aging" (time in culture) was relatively stable from early passages (2nd) to later passages (l0th); and (3) computer-assisted analysis of polypeptide differences between normal control cells (5th passage embryo cells) and various bisulfite transformed clones revealed both qualitative (6 proteins) and quantitative polypeptide differences between untreated control cells and each of the individual transformed clones. Following transformation three polypeptides (pI 5.9, MW 55 kDa; pI 5.4/53 kDa; and pI 5.4/32 kDa) were either not expressed or appeared as a charge-shift variant in each of the transformed lines. In addition to the apparent loss of expression or charge-shift two new polypeptides (pI 6.55/ 45 kDa and pI 5.90/26 kDa) were expressed in all clones and one polypeptide (pI 5.62/45 kDa) was expressed in all clones except clone A following transformation with either bisulfite or benzo[a]pyrene (BP). One polypeptide (pI 6.36/28 kDa) was expressed only in the BP transformed clone.